If you are aware of them, why don't you join an existing cooperative like Motion Twin? I would recommend go to one first before trying to make your own
In gamedev like in many other endeavor, I would not start a coop or a regular company without some experience or without at least a clear project in mind.
Like you said, there is no big capital investment in gamedev but there is still one: time. In a coop you are asking people to invest their own time in the hope that a few months down the line, a video game will be able to make a profit in a very competitive market. You have to give people reason to do it and to do it with you instead of going solo. That's how FOSS projects work.
You can lead the way: work a month on a project you would love and show people the result. It will be a WIP but as recruitment goes "help me finish that game" is easier to sell than "let's get together discuss what you want but I promise there will be profit down the line, but I haven't figured a business model yet"